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Crigler–Najjar syndrome or CNS is a rare inherited disorder affecting the metabolism of bilirubin, a chemical formed from the breakdown of the heme in red blood cells. The disorder results in a form of nonhemolytic jaundice, which results in high levels of unconjugated bilirubin and often leads to brain damage in infants. The disorder is inherited in an autosomal recessive manner. This syndrome is divided into types I and II, with the latter sometimes called Arias syndrome. These two types, along with Gilbert's syndrome, Dubin–Johnson syndrome, and Rotor syndrome, make up the five known hereditary defects in bilirubin metabolism. Unlike Gilbert's syndrome, only a few hundred cases of CNS are known. ==Type I== This is a very rare disease (estimated at 0.6–1.0 per million live births), and consanguinity increases the risk of this condition (other rare diseases may be present). Inheritance is autosomal recessive. Intense jaundice appears in the first days of life and persists thereafter. Type 1 is characterised by a serum bilirubin usually above 345 µmol/l (310–755) (whereas the reference range for total bilirubin is 2–14 μmol/l). No UDP glucuronosyltransferase 1-A1 expression can be detected in the liver tissue. Hence, there is no response to treatment with phenobarbital, which causes CYP450 enzyme induction. Most patients (type IA) have a mutation in one of the common exons (2 to 5), and have difficulties conjugating several additional substrates (several drugs and xenobiotics). A smaller percentage of patients (type IB) have mutations limited to the bilirubin-specific A1 exon; their conjugation defect is mostly restricted to bilirubin itself. Before the availability of phototherapy, these children died of kernicterus (bilirubin encephalopathy) or survived until early adulthood with clear neurological impairment. Today, therapy includes * exchange transfusions in the immediate neonatal period * 12 hours/day phototherapy * heme oxygenase inhibitors to reduce transient worsening of hyperbilirubinemia (although the effect decreases over time) * oral calcium phosphate and carbonate to form complexes with bilirubin in the gut * liver transplantation before the onset of brain damage and before phototherapy becomes ineffective at later age 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Crigler–Najjar syndrome」の詳細全文を読む スポンサード リンク
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